Hob



E. WILDHABER HOB Filed Dec. 50, 1922 May 19, 1925.

INVENTOR W ATTORN EY cutting edge.

' profile on the teeth of the hob having 4tooth of the blank. In a form hob, one

Patented May 19, 1925. Y1,538,772 UNITED STATES PATENT OFFICE.

ERNEST WILDHABER, OF BROOKLYN, NEW YORK, ASSIGNOB TO NILEB-BEMIENT-POND COMPANY, 0F NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

non.

imputation med December so, 1922. sensi no. 609,943.

To dll 'whom it may concern:

Be it known that I, ERNnsT WILDHABER, a lcitizen of the Republic of Switzerland, residing at Brookl n, in the county of Kings and State of7 New York, have invented' certain new and useful' Improvements in Hobs, of which the following is a specification. Y

vMy. invention relates to hobs and particularly to form `hobs for shaping milling cut-l ters.

One object of my invention is to provide a form hob having cutting edges inclined with respect to the hob axis for cut tin straight or helical `flutes on a blank.

nother object of my invention lis to ro` vide a form hob having teeth arrange in the form of a thread on a cylindrical body portion, the teeth having cutting edges inclined with respect to the hob axis and an end tooth of the hob having a finishing The hob, when operating on a blank, is sitioned with. respect to the blank so tltit the cutting ed e ou the iinishing cutting tooth is aligner? with a radialrblank` plane which is drawn perpendicularly to the hob axis. When so positioned with respectto a blank, the hob lcuts teethA having radially arranged cuttin faces.v However, liobs having cutting aces arranged perpendicularly to the axis thereof are not `suitable for cutting spiral fiutes or teeth having high cutting faces.

lIn a hob constructed in accordance with my invention, the teeth are arranged in the forni of a thread. on a cylindrical bod portion. The pitch of the hob teeth is pre erably made larger than the circular pitch of the blank taken on the outside diameter.v of the blank. The above statement refers especially to straight flutes on the blank. In the case of spiral fiutes on -the blank, the'pitch of the hob would be made larger than the corresponding pitch at a right angle to the fiutes. A finishing cuttin toothV is located at one end of the hob an such finishing tooth is provided with a finishing edge. The finishing edge is located in a rap dial blank plane which is not erpendicular to the axis of the hob. A blob, when'so constructed and so positioned with respect to the blank, serves to cut teeth having radially arranged cutting faces. The hob may be provided with undercut cutting faces on the `teeth thereof and cutspiral flutes Another object of my invention is to provide a forni hob of the above indicated character that shall have a pitch different from the circular pitch taken on the outside diameter of the blank to be cut.

A further object of' my invention is to provide a form hob havin teeth arranged in the form of a thread an having a pitch larger than the itch taken at the outside diameteriof the blank to be cut, the teeth having cutting edges inclined with respect to the hob axis and an end tooth of each a nishin cuttin edge.

The term form hob as use in this specification, is intended to cover a hob having a finishing cutting edge which cuts its own blank being may be constructed to on the blank or cut teeth having` undercut cutting faces. As above set orth, the pitch of the hob should be larger than the itch at the outside diameter of the blank). The hob del shaped. In hobs generally in use at the scribed and claimed .in this application is resent time, the teeth of a blank are shaped also 'shown and described in my copending y a generating operation. In a generatapplication Serial N o. 609,942 filed Decemin operation, a number of the teeth on a ber 30, 1922.' hoi serve to effect the finishing cut on each In the accompan ing drawing Figure l is a iagrammatic view illustrating a hob havin a pitch different from the blank pitch talen on the outside diameter of the blank. Fig. 2 is a plan view of the hob and blank shown in Fig. 1. A hob having the cuttin edges of the teeth perpendicular to the lio axis has some teeth have been arranged per endieularly ldrawbacks which limit its utility.L For exto the axis ofthe hob. A finishing cutting ample, a hob of this type is not suitable edge is formed on the end tooth of the hob. for cutting teeth of a very large size inas- 11e tooth effects a finishing cut on a whole face of each blank tooth. Reference may be made to my copending application Serial No. 609,941iiled December 30, 1922 for a further discussion of the term form hob.

Form hobs' have beenconstructed heretofore wherein the cutting faces on theV hob much as the helicoidal action of the hob tends to cut a convex surface on the teeth. Moreover, if such a hob were used to yform spiral flutes, a convex profile of a comparatively sharp curvature, would be formed on the blank teeth. The operation of a hob of this `type in cutting spiral flutes may be compared with the rinding of spiral kflutes by means of the p ain side of a grinding wheel. It is well known that it is impossible to grind spiral flutes with the p ain side of a grinding wheel and that only convex surfaces are produced which spoil the milling cutter being ground. In order to grind spiral flutes it is essential to provide a suitable conical grinding wheel. In accordance with the above reasoning, it is apparent that in order to cut spiral iutes, it 1s desirable to provide a hob having substantially straight cuttin edges which are inclined with respect to the axis o f the hob. Thus, it is necessary, or at least desirable, to provide a hob having cutting edges which are angularly disposed with respect to n.-

blank radiuslocated in a plane perpendicular to the hob axis. The operation of such a form hob is very similar to the operation -of a conical grinding wheel or V milling cutter.

Referring tothe accompanying drawing, a hob 1 is shown having teeth 2 formed on a cylindrical body portion 3. The hob is adapted to rotate in a counter-clockwise direction on an axis XY and is rovided with a finishing tooth 4. It will he'noted that the cutting edges on the teeth 2 are inclined with respect to the axis of the hob and are acc'ordingll1 suitable for cutting spiral flutes on a mi ing cutter blank. The hob is shown in engagement with a blank 5 having teeth 6.Y The blank is shown rotating on an axis C in a clockwise direction.

The inclined cutting edges of the hob 1 are obtained by forming the hob with a pitch p which is different from the pitch taken on the outside diameter of the blank 5. is larger than the circular pitch taken on t e outside diameter of the blank 5. In this regard, it may be noted that the pitch of a hob havin the cutting faces disposed perpendicular y to the hob axis is exactly equal to the pitch taken on' the out side diameter of the 4blank being operated u on. In the case of spiralv flutes on the bl)ank, the pitch referre to must be taken perpendicularly to the flutes.

Assuming the tooth 4 to be in a finishing position and the radial line C-7 to make an angle awith a radial plane per endicular to the axis of the hob, the pit'c of the rack corresponding to the hob 1 may be obtained in the manner disclosed in mypapplication Serial No. 609,941 filedDpcember A line is drawn through a point 7 y1011 the outside diameter of the blank 5 Luserna per Suc

is v a rack or a hob corresponding thereto is constructed as above indicated and is fed to the left as shown in Fig. 1 of the drawing, the teeth to the right of the finishing position shown lin Fig. 1 will not interfere with the radial profile of the blank tooth. The. hob is illustrated in position to finish one blank tooth as heretofore set forth. However, if the rolling motion; between the hob and blank were continued to the left beyond the illustrated position then an inof an involute would start at the osition illustrated in the drawing .and w len the tooth 4 was cutting along the line C-7.

The position of the tooth 4' is illustrated in Fig. l of the drawing as a limiting position when the hob is provided with a pitch along the line MN and correspondn to the circular pitch at a radius C--8. If the pitch should be made larger and the pitch line placed farther away from the axis of the b ank, the positions of the rack or hob teeth to the rig t of the illustrated position would not interfere with the radial face of the blank tooth taken valon aline C-7. Moreover, in such case the ilustrated position would not be the limiting position and the osition at which the generating of an invb ute would start. However, the changi'ng of the pitch in such manner would form 'larger flutes on the blank and'acc'rdingly as above set forth, by using a formv vvolute would be generated. The generation ameter of the blank,` it is possible to provide a hob with inclined cutting edges. cutting edges, as heretofore set forth, o rate in a manner similar to a cone grin ing wheel when operating on cutters having helical flutes.

It should be understood that such changes and modifications ma be made in m 1nvention as fall within the limits o the ap ended claims.

at I claim is: 1. A hob having one nishing cutting Such edge and comprising teeth arranged in the form of a thread on a' cylindrical body portion, the teeth having substantially straight cutting edges inclined with respect to the hob axis and the finishing cutting edge being located at the end of the hob.

2. A hob comprising teeth arranged in y teeth on the blank -member for cutting the form of a thread on a cylindrical body portion, the teeth having substantially straight cutting edges inclined with respect to the hob axis and the pitch of the hob di'ering :from the pitch of the teeth on the blank to be cut.

3. A hob comprising undercut teeth arranged in the form of a thread on a` cylindrical body member, the teeth having substantially straight cutting edges inclined with respect to the ho-b axis and the pitch of the hob differing from the pitch of the t0 be Cut.

4. A form hob having one finishing cutting edge and comprising teeth arranged in the form of a thread on a cylindrical body teeth having spiral flutes on a blank, the iinishing cutting edge being located at one end of the hob.

5. A form hob having one finishing cutting edge and comprising teeth arranged in the form of a thread on a cylindrical body member for cutting spiral flutes to form undercut teeth on a blank, the finishing cuttinbg edge being located at one end of the ho n 6. A form hob having one finishing, cutting edge and comprising teeth arranged in the form of a thread on a cylindrical body member for cutting spiral flutes to form undercut teeth on a blank, the teeth having substantially straight cutting edges inclined with respect to the blank axis.

7 A form hob having Vteeth arranged in the form of a thread, the teeth having substantially straight cutting edges inclined With respect to the hob axis and the pitch of the hob being larger than the pitch at the outside diameter of the blank.

8. A form hob having one iinishingcutting edge and comprising -teeth arranged in the form of a thread, the teeth having substantially straight cutting edges inclined with respect to the hob axis and the finishing cutting edge being located outside or inside an end toothon the hob according to the value of the hob pitch relative t0 the value of the pitch at the outside diameter of the blank.

In testimony whereof, l hereto affix my signature.

ERNEST WILDHABER. 

